1. Field of the Invention
This invention relates to vibration and shock activated valves, particularly earthquake activated valves.
A wide variety of valves have been proposed to shut off fluids after an earthquake.
Sunde in U.S. Pat. No. 4,131,124 teaches a valve that has a spring loaded plate that seals a valve when a pendulum in direct contact with the plate valve stem unseats. A problem common to this and other plate type valves is ensuring a gas-tight seal between the plate and the valve. The other problem is sealing back pressure that may build up. Plates tend to be one-way valves.
Brandon in U.S. Pat. No. 2,255,965 teaches a valve that is generally similar to that of Sunde. Brandon's device has the problem of bulkiness and difficulty in installation.
Hansen in U.S. Pat. Nos. 2,158,753 and 2,054,563 teaches two different valves where a pendulum activates a plate type valve. Both are bulky and are difficult to reset after a shock.
Poff in U.S. Pat. No. 4,094,332 teaches a valve generally similar to those of Sunde and Brandon. Again the shut-off mechanism is complex.
Bujold in U.S. Pat. No. 4,546,660 teaches a mechanism that is bolted onto a standard gas line that turns the valve when a pendulum responds to vibration. Again, the apparatus is bulky.
MacNeilage in U.S. Pat. No. 3,890,993 teaches a flat valve activated when a pendulum swings.
Suzuki in U.S. Pat. No. 4,201,536 teaches a pendulum that falls, triggering a mechanism that closes the fuel valve. The pendulum is held by three ball bearings. The device is bulky.
Earthquakes are a threat throughout much of the world, particularly including California and Japan. Aside from the damage caused by shaking, the earthquake frequently ruptures pipelines, thereby causing a severe fire hazard. In the 1906 San Francisco earthquake, it is said that more damage was caused by the fire subsequent to the earthquake than by the shaking caused by the earthquake. Therefore, it is important that the flow of natural gas in pipelines, as well as other gases or liquids, be automatically stopped as soon as the shaking occurs.
It would be advantageous to have a valve that rotated closed in response to shock or vibration. Such a valve could remain in the closed position despite back pressure. In particular, a valve that rapidly responded to shock is preferred.
It would be further advantageous to have a valve that rotated shut and was easily reset.
It would be advantageous to have a shock activated valve where the shock responsive portion of the device was mechanically independent of the valve position.